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Polymer-Nanoparticle Interaction as a Design Principle in the Development of a Durable Ultra-Thin Universal Binary Anti-Biofilm Coating with Long-Term Activity Yan Mei, Kai Yu, Joey C. Y. Lo, Lily E. Takeuchi, Narges Hadjesfandiari, Hossein YazdaniAhmadabadi, Donald E. Brooks, Dirk Lange, and Jayachandran N Kizhakkedathu ACS Nano, Just Accepted Manuscript • DOI: 10.1021/acsnano.8b05512 • Publication Date (Web): 24 Oct 2018 Downloaded from http://pubs.acs.org on October 25, 2018

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Polymer-Nanoparticle Interaction as a Design Principle in the Development of a Durable Ultra-Thin Universal Binary Anti-Biofilm Coating with Long-Term Activity

Yan Mei1,2, Kai Yu1,2, Joey C. Y. Lo3, Lily E. Takeuchi1,2, Narges Hadjesfandiari1,4, Hossein YazdaniAhmadabadi1,4, Donald E. Brooks1,2,4, Dirk Lange3, Jayachandran N. Kizhakkedathu1,2,4*

1Centre

for Blood Research, University of British Columbia, Vancouver, British Columbia V6T 1Z3,

Canada 2Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada 3Department of Urologic Sciences, University of British Columbia, Vancouver, British Columbia V5Z 1M9, Canada 4Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada

*Correspondence

and

requests

for

materials

should

[email protected])

1

ACS Paragon Plus Environment

be

addressed

to

J.N.K.

(email:

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Abstract: Bacterial attachment and biofilm formation pose major challenges to the optimal performance of indwelling devices. Current coating methods have significant deficiencies including the lack of long-term activity, easy of application and adaptability to diverse materials. Here we describe a coating method that could potentially overcome such limitations, and yield an ultra-thin coating with long-term antibiofilm activity. We utilized the interaction between polydopamine (PDA) nanoaggregates/nanoparticles and ultra-high molecular weight (uHMW) hydrophilic polymers to generate stable coatings with broad spectrum antibiofilm activity. We used a short-term bacterial adhesion assay as an initial screening method to identify coating compositions that give superior performance and found that only selected polymers (out of 13 different types) and molecular weights gave promising antifouling activity. Optimization of PDA self-assembly, polymer-PDA interaction and deposition on the surface using uHMW poly(N,N-dimethylacrylamide) (PDMA) (~795 KDa) resulted in a stable ultrathin coating (~19 nm) with excellent antifouling and antibiofilm properties (>4 weeks) against diverse bacteria (~108 CFU/ml) in shaking and flow conditions. The ultra-thin coating is effective on diverse substrates including metals and polymeric substrates. The uHMW PDMA is stabilized in the coating via supramolecular interactions with PDA, and generated a surface that is highly enriched with PDMA in aqueous conditions. Based on the surface analyses data, we also propose a mechanism for the stable coating formation. The molecular weight of PDMA is a crucial factor and only uHMW polymers generate this property. An attractive feature of the coating is that it does not contain any antimicrobial agents, and has the potential to prevent biofilm formation for diverse applications both short- and longterm.

Keywords: ultra-high molecular weight polymers, polymer-PDA interaction, antibiofilm, universal coating, long-term

2


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One of the key challenges associated with device/implant associated infection is the formation of bacterial biofilms within ~7 days of implantation which impede device/implant functions.1-6 Despite advancements in the development of antimicrobial and antibiofilm coating in recent years, current coating technologies to prevent biofilm formation fail to address all factors, including the prevention of biological deposition (proteins & organic molecules),7 inhibition of bacterial colonization, adaptation to diverse materials,8 easy application to devices of various sizes and shapes, and stability of the coating. Mussel-inspired surface chemistry is one of the most widespread strategies and has the potential to overcome most of the challenging issues in antibiofilm coating development.9-14 The strategies utilized to endow substrates with antibiofilm functions include via post-modification of PDA and the utilization of polymer-catechol conjugates.15-23 Although these strategies are versatile and universally applicable, none of these methods reported today showed promising long-term outcomes as a result of the formation of incomplete antifouling layer or limited surface coverage.24-29 The long-term antibiofilm activity is the key bottle necks in the advancement of mussel-inspired coating technologies. Most of the current antibiofilm coatings are short-lived, the short-term protein and bacterial adhesion on freshly-coated substrates are not predictive of their long-term antibiofilm behavior. As shown previously, in certain situations, some short-lived anti-biofilm coatings may actually function as bacterial reservoirs over the longer term and this will have important implications for their 3


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use in healthcare.30,31 Thus further methods are needed to prevent biofilm formation which can be easily applied to diverse substrates to generate long-term activity. Here, we report on a one-step dip coating surface modification method (Figure 1a) that makes use of polymer-polydopamine interaction to form an ultra-thin (~19 nm) and durable layer. We utilized a screening process to identify the molecular weights of the polymer and composition of the coating that generate broad spectrum antibiofilm activity and durability. We optimized the polydopamine (PDA) self-assembly and surface deposition process to generate a coating with excellent stability and exceptional antibiofilm performance. We show that a nano coating composed of uHMW PDMA in combination with PDA is highly effective in preventing the deposition of fouling proteins and biofilm formation in presence of >108 CFU/mL bacteria for prolonged periods of time (>4 weeks) in the absence of antimicrobial agents.

Results and Discussion Design and screening of binary antibiofilm coating. Our coating composition consist of two components: a surface anchoring agent PDA and an antifouling hydrophilic polymer. We initially screened a small library of hydrophilic polymers (Figure 1b and Table S1) with different molecular weights (MWs), chemistries and architectures in combination with dopamine in the binary coating to study their potential ability to prevent biofilm formation. For this, we utilized a high-throughput 964


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well polypropylene (PP) plate model (Figure 2a) and quantified initial Staphylococcus aureus (S. aureus) adhesion on the surface at 4 h time point, which is a crucial time point in the initiation of biofilm formation. Only select polymers with ultra-high molecular weight (uHMW) were found to prevent >99% of initial bacterial adhesion (Figure 2b). We then investigated the effect of polymer chemistry on early stage biofilm formation on PP film at 24 h utilizing scanning electron microscopy (SEM). Overall, the results (Figure 2c) showed early stage biofilm formation differ significantly with different uHMW polymers used, suggesting that the characteristics of the polymers present in the initial coating solution is crucial for the effective antifouling activity. Among the diverse uHMW polymers tested, PDMA was found to be the most efficacious, demonstrating >99.3% prevention of early stage biofilm formation. Based on this observation, we investigated the influence of MW of PDMA on biofilm formation by SEM imaging. The PDMAs with MWs ≥795 KDa provided highest resistance against early stage biofilm formation (Figure 2d1); only very few bacterial cells were observed on the PDA/PDMA-795K binary coating (Figure 2d2). Using this most efficacious polymer, we further investigated the influence of dopamine/PDMA ratio on antifouling performance of the coating. Overall, 1:5 dopamine/PDMA-795K ratio was found to provide the greatest resistance to S. aureus colonization (Figure 2e). To further characterize the coating, we determined the thickness by ellipsometry, chemical composition by X-ray photoelectron spectroscopy (XPS) and Attenuated Total Reflectance Fourier Infrared (ATR-FTIR) spectroscopy, as well as wettability by water contact angle measurements. The dry thickness of the coating was found to decrease with increasing MW of the PDMA, reaching 18.9 nm for 5


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PDMA-795K (Table S2). The surface composition showed that the coating became increasingly enriched with PDMA with increasing MW, as indicated by the increased ratio of nitrogen (N1s)/carbon (C1s) and C=O/C-OH (Figure S1). ATR-FTIR spectroscopy analysis supported the findings that uHMW PDMA was incorporated into the coating to a greater extent (Figure S2). As a consequence of hydrophilic polymer enrichment, the wettability of the surface is greatly improved with the use of uHMW PDMAs compared to the uncoated PP films (Figure S3). Universality and long-term stability of the coating. Next, we investigated the universality of the coating method and its application to diverse materials used in biomedical devices including titanium, polypropylene (PP), polyurethane (PU), polyethylene (PE), unplasticized polyvinyl chloride (uPVC), plasticized polyvinyl chloride (pPVC) and polyimide (PI). The application of the optimized coating (dopamine: PDMA-795K (1:5)) was evaluated using static water contact angle measurements (Figure 3a). Results show that all coated surfaces gave ~30° water contact angle irrespective of the substrate used. We analyzed early stage biofilm formation at 24 h on these diverse substrates modified with the optimized coating composition and demonstrated the prevention of bacterial adhesion (Figure 3b). Using titanium as the base material, we also analyzed the early stage biofilm resistance by multiple bacterial strains. The fluorescent microscopic images show that the optimized coating is able to prevent early biofilm formation by both Gram-positive and Gram-negative bacterial species including Staphylococcus saprophyticus (S. saprophyticus), Methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli (E. coli), and Pseudomonas aeruginosa (P. aeruginosa) (Figure 3c). Finally, the stability 6


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of the coating was investigated by measuring coating thickness after being stored in wet conditions for 3 weeks. No significant difference in coating thickness was noted (Figure 3d). The optimized coating also showed negligible thickness change after being exposed to 10 minutes ultrasonication or 20 minutes autoclaving process (Figure 3d). Subsequent biofilm studies verified that the coating maintained the antifouling properties following dry and wet storage, ultrasonication and autoclaving (Figure S4). The antifouling performance, long-term activity and biocompatibility of the optimized coating. One of the key elements driving indwelling device-associated infection and the failure of previously developed coatings is the deposition of a conditioning film on the material surface.32 Given this, future antifouling coatings need to be able to resist protein and bacterial deposition on the material surface. To address this important characteristic, we analyzed the deposition of bovine serum albumin (BSA) adsorption on the optimized coating using the quartz crystal microbalance with dissipation monitoring (QCM-D) method and by fluorescence microscopy using fluorescently labeled BSA and fibrinogen,24 two of the most commonly found components of urinary conditioning film.33 Overall, results from QCM-D analysis clearly showed our coating have superior antifouling activity; the amount of adsorbed BSA on the bare QCM chip was calculated to be 563.2±0.1 ng/cm2, while the coated chip resulted in a 17-fold decrease (38.1±0.2 ng/cm2) in BSA adsorption compared to the bare gold chip (Figure 4a). This superior antifouling activity also translated to polymeric substrates, as coating of unpolished PP films also resulted in a significantly lower levels of BSA and fibrinogen adsorption (91% and 88% decrease 7


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respectively) to the uncoated surface (Figure 4b and Figure S5-6). The anti-adhesion activity towards blood platelets was also further demonstrated (Figure S7), which indicated that the coating might be suitable for blood-containing devices including central venous catheters. One of the most significant challenge faced by the previously developed surface coating techniques is their ability to resist bacterial biofilm formation over the long-term.30 Considering that many indwelling devices need to remain biofilm free for long period of time, being able resist these detrimental bacterial layers from forming is vital. To investigate the ability of our PDA/PDMA-795K coating to resist bacterial biofilm formation, we exposed uncoated and coated surfaces to high concentration of S. aureus (>108 CFU/ml), a strong biofilm former associated with indwelling deviceassociated infections, in both shaking and flow conditions over a 3- and 4- week period respectively. Bacteria were allowed to adhere and colonize the materials for 24 h, after which time the culture was replenished daily to allow for efficient biofilm conditions. The level of biofilm formation was visualized over time using confocal and SEM microscopy. Using these analyses, we found biofilm formation to be reduced >99% on the ~19 nm thick PDA/PDMA-795K coated surfaces after 3 weeks of growth (Figure 4c). Similarly, using a flow model developed in our laboratory (Figure S8), we observed a very low number of single bacteria on the coated samples compared to the uncoated controls at the end of the 4-week incubation period, corresponding to a >97% reduction in bacterial biomass (Figure 4d). SEM analysis confirmed that the coated substrate resisted biofilm formation on the surface unlike the uncoated substrate which showed the development of micro colonies encased in EPS matrix on day 14 8


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and a more mature biofilm by day 28 (Figure 4e). The interaction between the coating and mammalian cells (fibroblasts) was further evaluated to determine the safety of the coating. The cells were spread nicely on the uncoated PS surface after 48 hours of incubation, however, almost no cells were adhered on the PDA/PDMA-795K coated PS substrate (Figure S9). Furthermore, the cell viability studies did not show any toxicity towards PDA/PDMA-795K solution even at considerably high concentration (1 mg/ml); all solutions showed cell viability in the range of 86-99% (Figure S10). Investigation on the mechanism of binary coating formation. The next step after demonstrating the superior antifouling activity and stability of our coating was to understand the mechanism behind its functionality and formation. Specifically, we were interested in determining how uHMW PDMA interact with PDA in the solution, how uHMW PDMA is incorporated into the coating, as well as the possible structure of the binary coating that provides long-term antifouling properties. To probe these facts, we initially investigated the particle formation in solution using dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements. The hydrodynamic size of the PDA particles without the PDMA was several micrometers as determined by DLS (Figure 5a). The aggregation of PDA particles following dopamine oxidation is prevented in presence of PDMA as evidenced by the smaller size of PDA particles formed under this condition. The hydrodynamic size of the PDA particles decreased to a few hundred nanometers in presence of uHMW PDMA. The TEM studies showed that PDA particles formed in the presence of PDMA-795K are evenly dispersed nanoparticles compared to the highly 9


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aggregated particles formed in the case of PDA alone (Figure S13).34-36 Furthermore, TEM analysis showed the formation of core-shell particles containing a dense PDA-core surrounded by a light shell layer of PDMA chains (Figure 5b).37,38 As suggested by previous reports, supramolecular interactions between PDA and PDMA might be contributing to the formation of the uniform dispersed particles.3942

The PDMA incorporated into PDA particles via hydrogen bonding and formed a core-shell structure

with PDMA shell and PDA core. In addition, it appears that the generated core-shell nanoparticle contains multiple nanoaggregates. To investigate the coating morphology, we used high resolution scanning electron microscopy (SEM) analysis. Our analyses of the PDA and PDA/PDMA coating by SEM point to the following process in the formation of the binary coating. In the case of PDA alone coating, we observed a two-layer coating: the top layer contains PDA nanoparticles about 100-200 nm in size while the bottom layer contains much smaller PDA nanoaggregates (Figure 5c) demonstrating a rough morphology. The coating became very uniform with low surface roughness in the presence of uHMW PDMA; the deposited layer only contains ultra-small nanoaggregates as revealed by SEM micrographs obtained at high resolution. AFM imaging also confirms similar surface structures in wet conditions (Figure S11). The PDA chemistry is still evolving and is under active investigation. The most recent findings suggest that dopamine initially generate oligomers via oxidation and then form PDA particles via a progressive self-assembly process.43,44 Based on this information and our current data, we propose a mechanism for the formation of thin coating in PDA alone and binary coating composed of PDA and 10


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uHMW PDMA (Figure 5d). We believe that the nanoscale coating formed on the substrate in our experimental conditions is during the dynamic assembly process in PDA polymerization. Our data from an experiment where we added PDMA-795K after the formation of PDA particles failed to generate a coating with sufficient thickness supports this argument (Table S2). The dopamine initially forms oligomers after oxidation via a covalent pathway, and the presence of uHMW PDMA is not affecting this process. In the next stage, the monomeric species and small oligomers initialize the surface anchoring along with the assembly in solution in an orderly manner to form nanoaggregates (about 220 nm). We suspect that this process might be influenced by the presence of uHMW PDMA. In the absence of PDMA, PDA nanoaggregates deposit onto the surface to form a tightly adhered bottom PDA layer and concurrently assemble in solution to form large PDA particles (about 100-200 nm in our system). The large PDA particles further deposit onto the surface to form a top layer with rough structures. The process of aggregation is uncontrolled in solution and form ultra large PDA aggregates (1000-10000 nm). However, in presence of uHMW PDMA, the PDA nanoaggregates deposit onto surface together with PDMA which further reorganize and form a stable layer on the surface. The PDA/PDMA nanoaggregates continue the self-assembly process in aqueous solution resulting in nanoparticles with a core-shell structure (about 100 nm in our system). The PDMA shell layer prevents the particles from further deposition and growth of a rough layer. The PDMA shell layer also prevent further aggregation of the PDA particles. Rearrangement of PDMA chains within the coating is occurring during the surface bonding process, resulting in overall enrichment PDMA on the surface due to high 11


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hydrophilicity of PDMA compared to PDA. The evidences here reveal that the uHMW PDMA is not simply incorporated into the coating but its presence dramatically changed the self-assembly process of the PDA and facilitate the formation of a uniform layer with PDMA.25,40 Dependence on the molecular weight. The results shown in Figure 2d demonstrate that molecular weight of PDMA plays a critical role on the coating’s anti-biofilm activity. Thus, we investigated the formation of PDA particles in presence of different molecular weight PDMAs. The amount of PDA generated in presence of PDMA is increased as evident from the increase in spectral intensity between 300-800 nm in the UV-Vis spectra (Figure 6a).45,46 This may be explained by the fact that dopamine alone generates PDA precipitates within several hours which blocks further polymerization and aggregation (Figure S12). The DLS and TEM analyses (Figure 6b and Figure S13) further proved that PDA particle aggregation was not completely blocked by using polymers with molecular weights around 43 KDa (PDMA-43K). This resulted in the formation of large PDA aggregates in the coating prepared in presence of PDMA-43K (Figure S14). Only uHMW PDMAs can prevent the aggregation and control the PDA self-assembly process, resulting in a much thinner and smoother anti-biofilm coating. To probe this further, we utilized AFM force measurements to determine the surface structure of the binary PDA/PDMA coating in wet conditions (Figure 6c). AFM approach curves showed a typical approach profile for steric repulsion exerted by polymer chains grafted on the surface (Figure 6c1); remanence of a brush layer.47,48 The equilibrium thickness of the coating increased with increasing MW of PDMA: reaching 25 nm, 45 nm and 90 nm respectively for PDMA-43K, PDMA-213K, PDMA-795K. The 12


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AFM retraction curve gave a characteristic profile of loop-like assembly of PDMA chains on the surface, and the adhesive force was found to decrease with increasing molecular weight of PDMA (Figure 6c2). Further, the extension length increased with increasing molecular weight of PDMA (Figure 6c3). Together these data support the hypothesis that the rearrangement of PDMA chains within the coating is occurring during the surface bonding process, resulting in overall enrichment of PDMA on the surface. Since PDMA is not covalently bound to PDA, the chains could rearrange to generate its optimal conformation. The increased content of PDMA chains on the surface of the coating generated the desired antifouling property. We have previously shown that PDMA is an excellent candidate to generate non-fouling surfaces.49-53 The PDA self-assembly in water and concurrent surface deposition depend on the molecular weight of PDMA. uHMW PDMA is crucial to generate loop-like assembly of hydrophilic chains to avoid fouling on the surface and polymers without uHMW (e.g. PDMA-43K) lack this property resulting in the generation a poor anti-fouling surface.

Conclusions In summary, we created a highly durable thin hydrophilic coating which prevents protein deposition and biofilm formation over the long-term (>4 weeks) in presence of high concentration of bacteria. Furthermore, this coating can easily be applied to diverse substrates, varying shapes and material properties via a dip coating process, and show broad spectrum bacterial adhesion resistance. We altered and optimized the self-assembly process in PDA nanoaggregate formation and PDA particle 13


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formation. The interaction of PDA and ultra-high molecular weight polymers, and the polymer chain reorganization within the coating is crucial in generating a durable surface coating with excellent antibiofilm activity. An attractive feature of the coating is that it does not contain any antimicrobial agents which have the potential to significantly increase the development and spread of antibiotic resistance.

Materials and Methods Polymer synthesis The hydrophilic polymers were synthesized based on previously described protocols.54 The molecular weight and polydispersity index (PDI) of polymers were determined using GPC. Detailed information is provided in Supporting Information. Coating process Unless stated otherwise, substrates were coated according to the protocol described here. The titanium deposited silicon wafers were exposed to oxygen plasma for 2 min to remove adventitious contamination. Other polymer substrates were cleaned by ultrasonication in deionized water for 10 min, dried under a steam of nitrogen. For a typical coating preparation process, a mixture of 2 mg/mL dopamine and 10 mg/mL polymer was prepared in 10 mM tris buffer (pH=8.5).9 For the PDA/PMPDSAH coating, polymer was dissolved in Tris-HCl buffer together with 5 mg/ml sodium chloride to promote 14


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the polymer dissolution. The substrates were then immersed in either dopamine alone or dopaminepolymer solution and were kept for 24 h without stirring. Afterwards, the modified samples were rinsed with Tris-HCl buffer and deionized water and dried in a steam of nitrogen. The modified substrates were used for further characterization. The 2 mg/ml preformed PDA particles and 10 mg/ml PDMA-795K combination was also used to coat the silicon wafer as a control. Particle and surface characterization The particle composites were characterized by dynamic light scattering, transmission electron microscopy, and ultraviolet–visible spectroscopy spectroscopy. The substrates were characterized by attenuated total reflectance Fourier transform infrared spectra, X-ray photoelectron spectroscopy, water contact angle measurements, ellipsometry, atomic force microscopy and scanning electron microscope. Detailed information is provided in the Supporting Information. Stability of the coating The stability of the coatings in physiological conditions was monitored measuring the thickness of the coating by ellipsometry measurements. The coated samples on silicon wafer were incubated in PBS buffer for different periods (3 days - 3 weeks), or ultrasonicated in PBS buffer for 10 mins, or autoclaved at 121°C for 30 mins before measuring the thickness change. The coated samples on titanium were also challenged with above mentioned procedures and evaluated for early stage biofilm formation protocol. Protein adsorption by QCM-D measurements 15


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QCM-D was used for evaluation of bovine serum albumin (BSA) adsorption on coatings. The coated gold sensors (PDA/PDMA-795K at ratio 1:5) were placed into the titanium flow chamber. PBS buffer was pumped over the sensor surface for 10 minutes and baseline equilibrium was reached. Then, the BSA solution in PBS (50 µg/ml) was pumped into the flow chamber for additional 15 min, followed by a PBS rinse for 10 min. The flow rate used for all steps was 0.05 ml/min, and the temperature was set to 22 °C. Biocompatibility assays The protocols for protein adsorption by fluorescence measurements, platelet adhesion, cell adhesion, and cell viability are provided in the Supporting Information. Initial bacterial adhesion measurements For initial bacterial adhesion screening assay, a 96-well PP plate format was used. The coating was prepared using different polymers on 96-well plate a composition of 1:5 dopamine and polymer in buffer. After the coating preparation, the 96-well plate was sterilized with 75% ethanol. Overnight culture of S. aureus lux strain was first adjusted to 106 CFU/mL in Lysogeny broth (LB) medium. Each well was equilibrated with LB for 10 min and then covered with 0.2 mL bacterial suspension. The inoculated plate was incubated for 4 h at 37°C. After the bacterial adhesion process, the wells were filled with PBS and washed twice to remove non-adherent bacteria. The wells with adhered bacteria were ultrasonicated for 10 min to release bacteria cells into PBS buffer (0.2 mL). The bacterial suspension was serially diluted and spread on an agar plate. After culturing overnight, the number of 16


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viable bacterial cells was quantified by counting the number of colonies on the agar plate. Early stage of biofilm formation Five different bacteria [Staphylococcus aureus lux strain (Xen36 Lux); Methicillin-resistant Staphylococcus aureus lux strain (USA300); Escherichia coli lux strain (DH5-α, plasmid pUC 19); Pseudomonas aeruginosa lux strain (PAO1 Tn7::Plac-lux); Staphylococcus saprophyticus strain (ATCC 15305)] were tested on diverse substrates to determine early stage biofilm formation. The coatings were applied to different substrates. The sterilized samples were cut into pieces and transferred into a 24-well plate. Overnight culture of bacteria was first adjusted to 106 cells/ml in LB. Each sample was equilibrated with LB for 10 min and then immersed in 1 mL S. aureus culture. The 24-well plate was incubated at 37 °C with shaking at 50 rpm. After 24 h incubation, suspension was removed and the samples were thoroughly washed PBS to remove loosely adhered bacteria. For the assessment of surface adhered bacteria, SYTO 9, a green-fluorescent nucleic acid staining agent, was used to label all the bacterial cells by penetrating cells membranes. The washed samples were soaked in a dye solution at room temperature in the dark for 15 min. The stained bacterial cells were viewed under a fluorescent microscope using the FITC filter. For SEM analysis, the samples were taken out and fixed with 2.5% glutaraldehyde for 2 h at 4 °C. After serial dehydration with 50%, 60%, 70%, 80%, 90%, and 100% ethanol for 10 min each, the samples were dried, coated with a thin layer of Au, and observed under SEM. The number of bacteria on the samples was quantified by counting the total number adhered bacteria from at least 6 representative images at the sample magnification. The results obtained from 17


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the coated samples were normalized using the adhered number from original uncoated samples. Long-term biofilm formation studies under shaking condition (50 RPM) Uncoated and coated titanium pieces were placed into 24-well plates for generating biofilm formation. A total volume of 1 ml Tryptic Soy Broth (TSB) culture containing 5*104 cells/mL S. aureus was added to each well. After every 24 hours, suspension was removed, the samples were slightly washed under shaking condition for 5 mins before new TSB culture with 5*104 cells/mL S. aureus was added. At day 1, day 3, day 7, day 14 and day 21, the samples were thoroughly washed and the fluorescent stain Syto-9 was used to microscopically assess the surface-attached biomass. The samples were analyzed using a confocal laser scanning microscope using the FITC 488 channel (Nikon Instruments Inc.). All images were acquired using identical acquisition settings. Long-term biofilm formation studies under flow condition For the flow condition, the uncoated and coated titanium pieces were inserted into the circulating tubes of a formally established flow model (Fig. S8) at 37°C.49 A flow rate of 114 mL/min was chosen based on the rotary pump RPM settings. A total volume of 500 ml LB culture containing 106 cells/ml S. aureus was added on day 0. The bacterial culture was totally replaced every day and circulated for 1 day, 3 days, 7 days, 14 days and 28 days before being drained from the loop. The bacterial concentration reach >108 cells/mL during the circulation. Finally, the substrates were removed, thoroughly washed, stained with Syto-9 and assessed using a confocal laser scanning microscope (FITC 488 channel, Nikon 18


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Instruments Inc.). All images were acquired using identical acquisition settings. The samples were also fixed and serial dehydrated for SEM analysis. Supporting Information The Supporting Information is available free of charge on the ACS Publications website at: The contents include: supporting experimental details; XPS data; ATR-FTIR spectra; water contact angle measurements; stability data; protein adsorption; platelet adhesion, flow set-up; cell adhesion; cell viability; photographs of different solutions; AFM images; TEM images; SEM images; detailed information on polymers and coating’s characterization.

Conflicts of interest YM, KY, DL, JNK are inventors on a patent application filled by University of British Columbia.

Acknowledgements This research is funded by the Canadian Institutes of Health Research (CIHR), Natural Science and Engineering Research Council (NSERC) of Canada and NSERC Collaborative Research and Training Experience Program for Regenerative Medicine (JNK). The authors thank the LMB Macromolecular Hub at the UBC Centre for Blood Research for use of the analytical facilities. Authors thank bio imaging 19


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facility at UBC and 4D labs at SFU for use of electron microscopy. The infrastructure facility is supported by Canada Foundation for Innovation (CFI) and the British Columbia Knowledge Development Fund (BCKDF). Y.M. is supported by NSERC CREATE program. N.H. is a recipient of a Health Canada/Canadian Blood Services graduate fellowship. J.N.K. is the recipient of a Career Investigator Scholar award from Michael Smith Foundation of Health Research. D.L. is the recipient of a New Investigator award from CIHR.

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Figure Captions:

Figure 1. Design of universal binary coating with antifouling performance. (a) Schematic of binary PDA/PDMA anti-biofilm coating deposition in aqueous conditions. Dopamine and PDMA-795K were mixed together in aqueous buffer and coating was applied via a simple dip coating process. The average thickness of the binary coating was around 19 nm. (b) Chemical structures of the library of hydrophilic polymers screened for the development of universal binary coating based on PDA and hydrophilic polymers (see also Table S1). PDMA: Poly(N,N-dimethylacrylamide), PAM: Polyacrylamide, PHMA: Poly(N-hydroxymethyl acrylamide), PHEA: Poly(N-hydroxyethyl acrylamide), PTHMAM: Poly(N-(tris(hydroxymethyl) methyl)acrylamide), PAAEGal: Poly(2 ′ -Acrylamidoethyl- β -D-galactopyranoside), PHPMA: Poly(N-(2-hydroxypropyl)methacrylamide), PMPDSAH:

Poly(N-(3-(methacryloylamino) propyl)-N,N-

dimethyl-N-(3-sulfopropyl) ammonium hydroxide), PMPC: Poly(2-methacryloyloxyethyl phosphorylcholine), PVP: Polyvinylpyrrolidone, PEO: Poly(ethylene oxide), HPG: Hyperbranched polyglycerol, Dextran. Figure 2. Investigation of S. aureus bacterial adhesion on diverse coatings. (a) Schematic of high throughput bacterial adhesion assay for diverse coatings. (b) Quantification of initial S. aureus adhesion on different polymers deposited 96-well PP plates after incubation in LB containing 106 cells/ml (initial concentration) for 4 h by CFU method. (c) Quantification of early stage S. aureus biofilm formation on different coatings composed of high molecular weight polymers and PDA deposited on PP films after incubation in LB containing 106 cells/ml (initial concentration) for 24 h. (d1) Quantification of early stage S. aureus biofilm formation on coatings composed of different molecular weight PDMA and PDA on PP films. The result shows a reduction of > 99.3% by use of the PDMA-795K. (d2) Representative SEM images of early stage of biofilm formation of S. aureus on uncoated PP films, PDA/PDMA-43K and PDA/PDMA795K coated PP films after 24 h incubation in LB medium. Scale bar is 20 µm. (e) Representative fluorescence microscopy images of early stage S. aureus biofilm formation on uncoated PP film, PDA: PDMA-795K (1:1) coated PP film, PDA: PDMA-795K (1:5) coated PP film, and PDA: PDMA-795K (1:15) coated PP film after 24 h incubation in LB medium. Scale bar is 100 µm. Green fluorescence represents all bacteria cells attached to the surface visualized using Syto-9 stain. Figure 3. Universality and long-term stability of the coating. (a) Water contact angles of uncoated and PDA/PDMA-795K coated substrates. Substrates include silicon, titanium, PP, PU, uPVC, pPVC, PI and PE. (b) Representative SEM images showing early stage biofilm formation on diverse uncoated and coated substrates after incubating in LB medium with S. aureus (initial concentration: 106 cells/ml) for 24 h. Scale bar is 5 µm. (c) Representative fluorescence microscopy images of early stage biofilm formation on uncoated and coated TiO2 after incubating in LB medium with S. saprophyticus (SS), Methicillin-resistant Staphylococcus aureus (MRSA), E. coli (EC), and P. aeruginosa (PA) for 24 h (initial concentration: 106 cells/ml). Scale bar is 100 µm. Green fluorescence represents all

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live bacterial cells attached to the surface visualized using Syto-9 stain. (d) Thickness evaluation of PDA/PDMA795K deposited coatings on silicon wafer after 0 day, 3 days, 1 week, 2 weeks and 3 weeks of incubation in PBS buffer, as well as 10 minutes ultrasonication and 20 minutes autoclaving process, as determined by ellipsometry. Figure 4. The antifouling performance and biocompatibilty of the optimized coating. (a) QCM-D frequency shift upon the adsorption of BSA on bare gold surface and PDA/PDMA-795K coated gold surface. After obtaining a stable PBS baseline for 10 min, the BSA solution (50 µg/ml) was injected for 15 min followed by a 10 min PBS wash. (b) Representative fluorescence images of uncoated and PDA/PDMA-795K coated PP films after fibrinogen adsorption. Uncoated and coated PP films were incubated with 0.25 mg/ml fibrinogen (Alex Fluor-594 conjugate) for 2 h and washed. Scale bar is 100 µm. (c1) Representative confocal fluorescence microscopy images of S. aureus biofilm formation on uncoated TiO2 and PDA/PDMA-795K coated TiO2 after 1 day, 3 days, 7 days, 14 days and 21 days incubation in TSB medium under shaking condition. Scale bar is 200 µm. Green fluorescence represents all bacterial cells attached to the surface visualized using Syto-9 stain. (c2) Calculated biomass accumulated on the surface under shaking condition. (d1) Representative confocal fluorescence microscopy images of S. aureus biofilm formation on uncoated TiO2 and PDA/PDMA-795K coated TiO2 after 1 day, 3 days, 7 days, 14 days and 28 days incubation in LB medium under flow condition. Scale bar is 200 µm. (d2) Calculated biomass accumulated on the surface under flow condition. (e) Representative SEM images of S. aureus biofilm formation on uncoated TiO2 and PDA/PDMA-795K coated TiO2 after 14 days and 28 days incubation in LB medium under flow condition. Scale bar is 5 µm. Statistical analysis: one-way analysis of variance (ANOVA) with Bonferroni multicomparison. ***: p

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